In recent years, there are many cases of processing holes with a high aspect ratio during fabricating a three-dimensional semiconductor memory. In this case, there is a problem that the hole is deformed in an arcuate shape (bowing shape) as the processing time increases. For this reason a protective film may be formed on a surface of the hole at the time of processing the hole. When the etching resistance of the protective film is too low, however, the protective film may be chipped off. Further, when the etching resistance of the protective film is too high, the protective film may block the hole.